Plasma etching methods

ABSTRACT

A patterned organic masking layer is formed outwardly of a feature layer to be etched. It has at least one feature pattern having a minimum feature dimension of less than or equal to 0.3 micron. The feature layer has a thickness which is to be etched to form the one feature pattern in the feature layer. The feature pattern is plasma etched into the feature layer using the masking layer as a mask. The plasma etching comprises at least one etching segment where at least 30% of said thickness of the feature layer is etched using an etching gas comprising one gas compound comprising carbon, hydrogen and at least one halogen present at greater than or equal to 70% concentration by volume as compared to all carbon, hydrogen and halogen containing gas compounds in the etching gas. Such plasma etching is conducted under conditions effective to produce at least that portion of the one feature pattern in the feature layer formed during the one etching segment to have a sidewall taper, if any, of less than or equal to 5° and an organic masking layer top outer surface roughness proximate the feature pattern at a conclusion of the etching segment which is characterizable by an average value less than 100 Angstroms. Such value is determinable by scanning electron microscopy as an average maximum size of all surface discernible objects of the patterned masking layer as measured and averaged along any 0.3 micron length of top outer surface from the one feature pattern. Other implementations are also contemplated.

TECHNICAL FIELD

This invention relates to plasma etching methods.

BACKGROUND OF THE INVENTION

Integrated circuitry density continues to increase and featuredimensions continue to get smaller. One aspect of semiconductorintegrated circuitry fabrication is the etching of contact openingsthrough insulating layers, such as borophosphosilicate glass (BPSG), toexpose inward circuit regions to which electrical connection is desired.

Contact openings are typically presently formed by depositing an organicmasking layer (photoresist, being one example) outwardly of the layerwithin which the opening is to be formed. The masking layer is patternedto leave desired contact openings therethrough while leaving other areasof the layer covered (i.e., masked) such that etching will not thereoccur. The insulating layer is thereafter etched through the organicmasking layer openings, preferably highly selectively to remove theinsulating layer at a substantially greater rate than any etching of themasking layer. The ultimate goal is to outwardly expose a desired regionof the underlying substrate.

Forming such openings is preferably conducted using a highly anisotropicetch, such as a plasma etch. One such prior art etch employs an AppliedMaterials IPS Dielectric Etcher using reactive gas flows of CHF₃ andCH₂F₂ at a volumetric ratio of 11:9, respectively. It was discoveredusing such chemistry that as the minimum feature dimension of thecontact opening fell to 0.3 micron and below, the etched sidewalls ofthe feature layer being etched were becoming striated or otherwiseroughened to a degree sufficient to impact critical dimension (CD) ofthe feature and overall yield. Such roughening apparently resulted fromformation of striations or other roughenings in the opening sidewalls ofthe photoresist, which were being mask transferred to the feature layer.Such roughening was more prone to occur in useful processing windows inhigh density deposition tools, namely in processing windows whereacceptable uniformity across the substrate could be achieved. Suchsidewall striations might also have occurred in etching of largercontact openings, but were not problematic due to the larger openingdimensions. However at the 0.3 micron level and below, roughened orotherwise striated sidewalls within a feature opening (i.e., a damascenetrough, a contact opening or other feature) can adversely affect CD andyield.

The invention was motivated in addressing and overcoming this particularproblem, yet is not so limited. Aspects of the invention are seen tohave applicability to other aspects of plasma etching, with theinvention only being limited by the accompanying claims, appropriatelyinterpreted in accordance with the Doctrine of Equivalents.

SUMMARY

The invention comprises plasma etching methods. In one implementations,a patterned organic masking layer is formed outwardly of a feature layerto be etched. The patterned organic masking layer has at least onefeature pattern having a minimum feature dimension of less than or equalto 0.3 micron. The feature layer has a thickness inwardly of the onefeature pattern which is to be etched to form the one feature pattern inthe feature layer. The at least one feature pattern is plasma etchedinto the feature layer using the organic masking layer as a mask. Theplasma etching comprises at least one etching segment where at least 30%of said thickness of the feature layer is etched using an etching gascomprising one gas compound comprising carbon, hydrogen and at least onehalogen present in the etching gas at greater than or equal to 70%concentration by volume as compared to all carbon, hydrogen and halogencontaining gas compounds in the etching gas. Such plasma etching isconducted under conditions effective to produce at least that portion ofthe one feature pattern in the feature layer formed during the oneetching segment to have a sidewall taper of less than or equal to 5° andan organic masking layer top outer surface roughness proximate thefeature pattern at a conclusion of the etching segment which ischaracterizable by an average value less than 100 Angstroms: Suchaverage value is determinable by scanning electron microscopy as anaverage maximum size of all surface discernible objects of the patternedmasking layer as measured and averaged along any 0.3 micron length oftop outer surface from the one feature pattern.

Other implementations are also contemplated.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a diagrammatic sectional view of a semiconductor waferfragment in process in accordance with an aspect of the invention.

FIG. 2 is a view of the FIG. 1 wafer fragment at a processing stepsubsequent to that depicted by FIG. 1.

FIG. 3 is a view of the FIG. 1 wafer fragment at a processing stepsubsequent to that depicted by FIG. 2.

FIG. 4 is a diagrammatic sectional view of an alternate embodimentsemiconductor wafer fragment at a processing step in accordance with anaspect of the invention.

FIG. 5 is a diagrammatic sectional view of an example high densityplasma etcher usable in accordance with an aspect of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

FIG. 1 illustrates a wafer fragment to be etched indicated generallywith reference numeral 10. Such comprises a bulk monocrystalline siliconsubstrate 12 having an exemplary diffusion region 14 formed therein. Inthe context of this document, the term “semiconductor substrate” or“semiconductive substrate” is defined to mean any constructioncomprising semiconductive material, including, but not limited to, bulksemiconductive materials such as a semiconductive wafer (either alone orin assemblies comprising other materials thereon), and semiconductivematerial layers (either alone or in assemblies comprising othermaterials). The term “substrate” refers to any supporting structure,including, but not limited to, the semiconductive substrates describedabove. Alternate substrates from substrate 12 are of course usable inthe invention.

A feature layer 16 to be plasma etched is formed outwardly of substrate12. In the preferred and reduction-to-practice examples, the feature tobe etched within layer 16 is in the form of a contact opening, withlayer 16 predominately comprising silicon dioxide, such as BPSG. Theinvention is not, however, in any way limited to contact openingformation nor to etching into predominately silicon dioxide comprisinglayers. Aspects of the inventions are applicable to etching otherfeatures, by way of example only, damascene trough lines in insulativematerials, polysilicon conductive features, and etching of othermaterials (i.e., Si₃N₄) to produce features in the form of openings orprojections, whether conductive or not conductive. An organic maskinglayer 18 is formed outwardly of feature layer 16, and is patterned toform the desired feature patterns therethrough. One example organicmasking layer is a photoresist, such as SEPR 402 available fromSHIN-ITSU of Tokyo, Japan. Masking layer 18 has a top outer surface 17.Exemplary thicknesses for layers 16 and 18 are 21,000 Angstroms and8,300 Angstroms, respectively.

An exemplary feature pattern in the form of a contact opening 20 isformed in layer 18, and in preferred implementations has some minimumfeature dimension A which is less than or equal to 0.3 micron. Also forpurposes of the continuing discussion, feature layer 16 has somethickness B inwardly of feature pattern 20 which is to be etched to formthe one feature pattern in feature layer 16. Of course almostuniversally, identical and/or other features are being etched elsewherein layer 16, with only a single feature 20 being shown for example.

Referring to FIGS. 2 and 3, the at least one feature pattern 20 inorganic masking layer 18 is plasma etched into feature layer 16 usingorganic masking layer 18 as a mask to form a feature 22. The plasmaetching comprises at least one etching segment C where at least 30% ofthickness B (FIG. 1) of feature layer 16 is etched using an etching gascomprising one gas compound comprising carbon, hydrogen and at least onehalogen present in the etching gas at greater than or equal to 70%concentration by volume as compared to all carbon, hydrogen and halogencontaining gas compounds in the etching gas. The one etching segmentpreferably comprises high density plasma, which in the context of thisdocument is defined to mean any plasma etching achieving a density of atleast 10⁹ ions/cm³. An example reactor is a dual source, high densityplasma etcher such as an IPS Dielectric Etcher from Applied Materials,Inc., of Santa Clara, Calif. Other type etching tools are also of coursecontemplated such as, by way of example only, parallel plate etchersthat have one or more power supplies and/or etchers that use magneticfields to affect the motion of charged species inside the chamber.

FIG. 2 illustrates approximately 80% of thickness “B” of layer 16 beingetched in the one etching segment, with only a little reduction in thethickness of organic masking layer 18 occurring during the etch astypically occurs with such layer during high density plasma etching. Theinvention also of course contemplates other percentages of thicknessbeing etched. Further, and by way of example only, the plasma etchingcan comprises only one etching segment where 100% of the thickness ofthe feature layer is etched using said etching gas.

Preferably, the one gas compound is present in the etching gas atgreater than or equal to 80% concentration by volume as compared to anyother carbon, hydrogen and halogen containing gas compound(s) in theetching gas during the one etching segment. Even more preferably, suchgas is present at a 90% concentration by volume, as compared to anyother carbon, hydrogen and halogen containing gas compound in theetching gas during the one etching segment. Even more preferably, suchgas is present at a 95% concentration by volume, as compared to anyother carbon, hydrogen and halogen containing gas compound in theetching gas during the one etching segment. Even more preferably, suchgas is present at a 100% concentration by volume, as compared to anyother carbon, hydrogen and halogen containing gas compound(s) in theetching gas during the one etching segment. An example preferred gascompound is CH₂F₂. An example additional gas compound comprising carbon,hydrogen and at least one halogen present in the etching gas at lessthan 30% concentration with the CH₂F₂ is CHF₃. The plasma etching duringthe one segment is preferably void of any etching gases havingcarbon-nitrogen bonds, carbon-oxygen bonds, and oxygen-oxygen bonds.

Plasma etching during the one segment is most preferably effective toproduce at least that portion of feature pattern 22 in feature layer 16formed during the one plasma etching segment to have a sidewall taper,if any, of less than or equal to 5°, with a preferred lack of taperessentially being depicted in FIGS. 2 and 3. Further most preferably andin accordance with what motivated the invention, top outer surface 17 oforganic masking layer 18 will have a roughness proximate feature pattern20 at a conclusion of the one etching segment which is characterizableby an average value less than 100 Angstroms. This average value isdeterminable by scanning electron microscopy as an average maximum sizeof all surface discernible objects of patterned masking layer 18 asmeasured and averaged along any 0.3 micron length D (FIG. 2) of topouter surface 17 from feature pattern 20. More preferably, the averagesurface roughness value is less than or equal to 50 Angstroms.

Top outer surface roughness created by the plasma etching has beendetermined to be of some significance in the sidewall roughness ofmasking layer 18 within feature pattern opening 20, particularly in theimplementations where using an etching gas comprising one gas compoundcomprising carbon, hydrogen and at least one halogen present in theetching gas at greater than or equal to 70% concentration by volume ascompared to all carbon, hydrogen and halogen containing gas compounds.Regardless, and although somewhat undesirable, the combination of arough top outer masking layer surface and smooth masking layer featuresidewalls was not observed in reduction-to-practice examples, and wasalso not observed when operating below the above stated 70%concentration. At and above the above stated minimum 70% concentration,power parameters can be readily selected, if desired, by a person ofskill in the art to arrive at a sidewall roughness which matches orshadows that of the top surface roughness.

Further, it was observed in reduction-to-practice examples that themasking layer sidewall roughness which was the determining factor inetched feature layer sidewall roughness/striations (and attendant CDchange) was that closest to the feature layer. Roughness or striationsformed by the etching in the masking layer adjacent the top outersurface but not where the masking layer joins the feature layer did notmask transfer into the feature layer.

Referring more specifically to FIG. 3, plasma etching is furtherconducted to comprise another etching segment E which is conducted afterthe one etching segment, and which is not necessarily the same as theone segment. Accordingly, such further etching may or may not increaseroughness in the sidewalls of materials 16 and 18. Most preferably, thedegree of further etching (i.e., conditions and time of etch) is notsufficiently great such that the sidewall smoothness of layer 16 createdby etching segment C is maintained at the conclusion of the finalillustrated etching and also occurs in etching segment E. In thedescribed embodiment, an example additional etching segment E would usean etching gas comprising CH₂F₂ and CHF₃, with the CHF₃ being present atgreater than 30% by volume of a total of the CH₂F₂ and CHF₃ gases.

The above-described first embodiment had the organic masking layercomprising photoresist with the average maximum value of the organiclayer top outer surface roughness being that of the photoresist topouter surface at the conclusion of the one etching segment. FIG. 4illustrates an alternate embodiment 10 a. Like objects from the firstdescribed embodiment are depicted with the same numerals, withdifferences being depicted by the suffix “a” or with different numerals.In certain etching applications, the plasma etching can result inanother organic masking material layer forming over the depletingoriginal organic masking layer 18 during etching. In the context of thisdocument, “organic” defines any material containing carbon bonded withat least some other elements which are not carbon. FIG. 4 depicts theetching proceeding whereby another organic material layer 19 forms overmasking layer 18 during the etching. This layer is formed and removedduring the etching and can achieve a nearly constant steady statethickness, or it may be formed and removed as the etching proceeds. Thislayer is shown in FIG. 4 as forming on the surface of the underlyinglayer mask layer and on the mask sidewalls. Some taper (less than orequal to 5 degrees) usually accompanies the growth of the layer on themask sidewall. Both the formation on the surface of the mask and on thesidewalls of the mask can eliminate or postpone the eventual reformationof rough mask sidewalls and the transfer of this roughness into featurefilm 16. In the context of this example, the average maximum value ofthe organic layer top outer surface roughness will be that of surface 17a of the another organic masking material 19, and not that ofphotoresist where layer 18 comprises photoresist.

Further in the FIG. 4 example, masking layer 18 might constitute aninorganic material, with organic material 19 forming thereover at leastduring the one etching segment. By way of example only, preferredinorganic masking materials include, polysilicon, silicides and metals.

The FIGS. 1-3 example also depicts the one etching segment C as beingconducted at the start of the plasma etching, and not conductedthroughout all of the plasma etching. Alternately by way of exampleonly, the one etching segment could be conducted from the startthroughout all of the plasma etching. Further alternately by way ofexample only, the one etching segment could be conducted at the end ofthe plasma etching, and not otherwise conducted throughout all of theplasma etching. Further alternately by way of example only, the oneetching segment could be conducted between the start and the end of theplasma etching, and not conducted at either the start or the end of theplasma etching. In one implementation, it has been discovered thatconducting a later-in-time etching in accordance with theabove-described preferred 70% or greater concentration results insmoothing of sidewall roughness in the feature layer occurring from anearlier-in-time plasma etching having less than 70% concentration of thesubject gas.

Accordingly, one aspect of the invention contemplates plasma etching atleast one feature pattern into the feature layer using the organicmasking layer as a mask comprising first-in-time and second-in-timeetching segments. In a first-in-time of the etching segments, an etchinggas is utilized which comprises at least two gas compounds with eachcomprising carbon, hydrogen and at least one halogen, and each beingpresent in the etching at greater than 30% concentration by volume ascompared to all carbon, hydrogen and halogen containing gas compounds inthe etching gas. The first etching segment produces a first degree ofsidewall roughness along a sidewall portion of the one feature patternbeing formed in the feature layer. A second etching segment is conductedafter the first etching segment, with the second etching segmentcomprising etching at least 30% of the thickness of the feature layerusing an etching gas comprising at least one gas compound present atgreater than or equal to 70% concentration by volume as compared to allcarbon, hydrogen and halogen containing compounds in the etching gaseffective to smooth the sidewall roughness of the first degree to asmoother second degree, for example to less than 250 Angstroms or lessthan 100 Angstroms. Typically and preferably, the one gas compound inthe second etching segment is one of the at least two gas compoundsutilized in the first etching segment.

In one implementation, the invention contemplates plasma etching the atleast one feature pattern into the feature layer using the organicmasking layer as a mask comprising first-in-time and second-in-timeetching segments. In a first-in-time of the etching segments, an etchinggas is utilized which comprises at least two gas compounds with eachcomprising carbon, hydrogen and at least one halogen and each beingpresent in the etching gas at greater than 30% concentration by volumeas compared to all carbon, hydrogen and halogen containing gas compoundsin the etching gas. The first etching segment produces a first degree oftop surface roughness of the organic masking layer A second etchingsegment is conducted after the first etching segment, with the secondetching segment comprising etching at least 30% of said thickness of thefeature layer using an etching gas comprising at least one gas compoundpresent at greater than or equal to 70% concentration by volume ascompared to all carbon, hydrogen and halogen containing gas compounds inthe etching gas effective to smooth the organic masking layer topsurface roughness of the first degree to a smoother second degree. Inonly a preferred aspect of this implementation, the first segmenteffectively produces a rough top, and also rough sidewalls but onlyproximate the top in the masking layer. The second segment thenpreferably smooths the top and largely precludes the sidewall roughnessfrom being transferred into the film by stopping masking layer sidewallroughness from migrating downward to adjacent the feature layer.

In one implementation, the plasma etching comprises a plurality ofetching segments which total at least 30% of the thickness of thefeature layer being etched. The plurality of etching segments use anetching gas comprising one gas compound comprising carbon, hydrogen andat least one halogen present in the etching gas at greater than or equalto 70% concentrations (i.e., not necessarily the same concentration ineach segment) by volume as compared to all carbon, hydrogen and halogencontaining gas compounds in the etching gas. Preferably, each etchingsegment of the plurality removes at least 1000 Angstroms of featurelayer thickness. The plasma etching also comprises at least oneintervening etching segment which is not one of the plurality. Theintervening etching segment comprises using an etching gas comprising atleast two gas compounds with each comprising carbon, hydrogen and atleast one halogen and each being present in the etching gas at greaterthan 30% concentration by volume as compared to all carbon, hydrogen andhalogen containing gas compounds in the etching gas. The plurality ofetching segments, with the intervening segment(s) is effective toproduce at least that portion of the one feature pattern in the featurelayer to have a sidewall taper, if any, of less than or equal to 5° andan organic masking layer top outer surface roughness proximate thefeature pattern at a conclusion of said plurality of etching segmentswhich is characterizable by an average value less than 100 Angstroms asis determinable by scanning electron microscopy as an average maximumsize of all surface discernible objects of the patterned masking layeras measured and averaged along any 0.3 micron length of top outersurface from the one feature pattern.

FIG. 5 is a cross-sectional schematic view of one form of a plasmaetcher 200, particularly an IPS Dielectric Etcher from AppliedMaterials, Inc., of Santa Clara, Calif. The illustrated plasma etcher200 includes a chamber 203 defined by an RF window 205, an enclosure207, a hot ring 209, and a substrate assembly chuck 211. The substrateassembly chuck 211 includes a collar 213 and a ceramic base 215 tosupport a substrate 217, such as a silicon wafer or other substrate.Exhaust ports 219 are defined by gaps between the enclosure 207 and thehot ring 209, and connect to exhaust chambers 221. The RF window 205 andthe hot ring 209 are maintained at selected temperatures with respectivetemperature controllers 261, 263. The temperatures of the RF window 205and the hot ring 209 are typically maintained between 120-200° C. and150-300° C., respectively. The RF window 205 and the enclosure 207 maybe made of either silicon (Si) or silicon carbide (SiC) or a combinationthereof, the hot ring 209 may be made of quartz, and the collar 213 maybe made of silicon carbide. Silicon, especially when heated, can removeor “getter” fluorine from the chamber 203 and thus can alter thecomposition of a fluorine containing gas mixture if included in thechamber 203.

In this etcher, a first set of induction coils 233 and a second set ofinduction coils 235 are coaxially placed in proximity to the RF window205, with the second set 235 placed within the first set 233. RFgenerators 239, 237 connect to the first and second set of inductioncoils 233, 235, respectively. An RF bias generator 241 is provided thatconnects to the substrate assembly chuck 211. RF excitations (RFvoltages or currents) from the RF generators 239, 237 are applied to thefirst and second sets of induction coils 233, 235, respectively, andproduce oscillating electric and magnetic fields at the RF window 205.The RF window 205 and the chamber walls 207 in this example aregrounded. Because the RF window 205 is at least partially electricallyconducting, the RF window 205 shields the chamber 203 from theoscillating electric fields produced by the coils 233, 235. Theoscillating electric fields are either attenuated by or, in some cases,totally blocked by the RF window 205. As a result of the shieldingeffect of the RF window 205, the oscillating magnetic field produced bythe coils 233, 235 is primarily responsible for the generation of aplasma in the chamber 203. The RF generators 237, 239 in the illustratedetcher provide RF excitations at typical frequencies of between about1.0-3.0 MHz.

A gas inlet 251 is connected to a gas supply manifold 253. Gases, whichmay be gas mixtures, for the chamber 203 are mixed at the gas manifold253 and supplied to the chamber 203 through a gas inlet 251. A vacuumpump 255 is situated to evacuate the chamber 203 and is connected to thechamber 203 via a valve 256. During etching, the pressure in the chambermay generally be maintained in the range of from about 2 mTorr to 50mTorr.

Example specific parameters utilizing this reactor and CH₂F₂ and CHF₃gases for the one etching segment are as follows. CH₂F₂ flow ispreferably at from about 45 to about 55 sccm, with CHF₃ flow preferablybeing from 0 to about 15 sccm. Outer power is preferably kept at from620 to 760 watts, with inner power ranging from 105 to 140 watts.Substrate bias is preferably kept at between 600 and 740 watts. Thetemperature of the reactor roof is preferably kept at from 130° to 150°C., while that of the ring is kept at from 180° to 220° C. The backsideof the substrate is preferably cooled to from between −20° C. and +10°C. Reactor pressure during deposition is preferably at or about 25mTorr.

In a first specific reduction-to-practice example, outer power was 725Watts, inner power was 125 Watts, and bias power was 700 Watts. Gas flowwas 100% CH₂F₂ at 35 sccm. Chuck temperature was −10° C., windowtemperature at 140° C., and ring temperature at 200° C. Reactor pressurewas 25 mTorr. Time of etch was 100 seconds, and the depth of the etchwas 1.2 micron. The top outer surface value for smoothness/roughness wasless than 10 Angstroms. The material etched was BPSG.

In a second specific reduction-to-practice example, outer power was 900Watts, inner power was 100 Watts, and bias power was 665 Watts. Gas flowwas CH₂F₂ at 50 sccm, CF₄ at 1 sccm and CHF₃ at 1 sccm. Chucktemperature was −10° C., window temperature at 140° C., and ringtemperature at 200° C. Reactor pressure was 25 mTorr. Time of etch was100 seconds, and the depth of the etch was 1.1 micron. The top outersurface smoothness/roughness value was less than 10 Angstroms. Thematerial etched was BPSG.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

What is claimed is:
 1. A plasma etching method comprising: forming apatterned organic masking layer outwardly of a feature layer to beetched, the patterned organic masking layer having at least one featurepattern having a minimum feature dimension of less than or equal to 0.3micron, the feature layer having a thickness; and plasma etching the atleast one feature pattern into the feature layer using the organicmasking layer as a mask, the plasma etching comprising at least oneetching segment where at least 30% of the thickness of the feature layeris etched using an etching gas comprising one gas compound comprisingcarbon, hydrogen and at least one halogen present in the etching gas atgreater than or equal to 70% concentration by volume as compared to allcarbon, hydrogen and halogen containing gas compounds in the etching gaseffective to produce at least that portion of the one feature pattern inthe feature layer formed during the one etching segment to have asidewall taper, if any, of less than or equal to 5° and an organicmasking layer top outer surface roughness proximate the feature patternat a conclusion of the one etching segment which is characterizable byan average value less than 100 Angstroms as is determinable by scanningelectron microscopy as an average maximum size of all surfacediscernible objects of the patterned masking layer as measured andaveraged along any 0.3 micron length of top outer surface from the onefeature pattern, wherein the organic masking layer comprisesphotoresist, and another organic masking material layer formingthereover during the plasma etching, the average maximum value of theorganic layer top outer surface roughness being that of the anotherorganic masking material top outer surface and not that of thephotoresist.
 2. The method of claim 1 wherein the plasma etchingcomprises only one etching segment where 100% of the thickness of thefeature layer is etched using said etching gas.
 3. The method of claim 1wherein the organic masking layer comprises photoresist, the averagemaximum value of the organic layer top outer surface roughness beingthat of the photoresist top outer surface.
 4. The method of claim 1wherein the one feature pattern comprises a contact opening.
 5. Themethod of claim 1 wherein the feature layer comprises SiO₂.
 6. Themethod of claim 1 wherein the feature layer comprises Si₃N₄.
 7. Themethod of claim 1 wherein the one gas compound is present in the etchinggas at greater than or equal to 80% concentration by volume as comparedto any other carbon, hydrogen and halogen containing gas compound(s) inthe etching gas during the one etching segment.
 8. The method of claim 1wherein the one gas compound is present in the etching gas at greaterthan or equal to 90% concentration by volume as compared to any othercarbon, hydrogen and halogen containing gas compound(s) in the etchinggas during the one etching segment.
 9. The method of claim 1 wherein theone gas compound is present in the etching gas at greater than or equalto 95% concentration by volume as compared to any other carbon, hydrogenand halogen containing gas compound(s) in the etching gas during the oneetching segment.
 10. The method of claim 1 wherein the one gas compoundis present in the etching gas at 100% concentration by volume ascompared to any other carbon, hydrogen and halogen containing gascompound(s) in the etching gas during the one etching segment.
 11. Themethod of claim 1 wherein the one gas compound is CH₂F₂.
 12. The methodof claim 1 wherein the average value of roughness is less than or equalto 50 Angstroms.
 13. The method of claim 1 wherein the one etchingsegment comprises high density plasma.
 14. The method of claim 1 whereinthe one etching segment is conducted at the start of said plasma etchingand is not conducted throughout all of said plasma etching.
 15. Themethod of claim 1 wherein the one etching segment is conducted at theend of said plasma etching and is not conducted throughout all of saidplasma etching.
 16. The method of claim 1 wherein the one etchingsegment is conducted between the start and the end of said plasmaetching, and not conducted at the start or end of said plasma etching.17. The method of claim 1 wherein the plasma etching during the onesegment is void of any etching gases having carbon-nitrogen bonds. 18.The method of claim 1 wherein the plasma etching during the one segmentis void of any etching gases having carbon-oxygen bonds.
 19. The methodof claim 1 wherein the plasma etching during the one segment is void ofany etching gases having oxygen-oxygen bonds.
 20. A plasma etchingmethod comprising: forming a patterned organic masking layer outwardlyof a feature layer to be etched, the patterned organic masking layerhaving at least one feature pattern having a minimum feature dimensionof less than or equal to 0.3 micron, the feature layer having athickness; and plasma etching the at least one feature pattern into thefeature layer using the organic masking layer as a mask, the plasmaetching comprising at least one etching segment where at least 30% ofthe thickness of the feature layer is etched using an etching gascomprising one gas compound comprising carbon, hydrogen and at least onehalogen present in the etching gas at greater than or equal to 70%concentration by volume as compared to all carbon, hydrogen and halogencontaining gas compounds in the etching gas effective to produce atleast that portion of the one feature pattern in the feature layerformed during the one etching segment to have a sidewall taper, if any,of less than or equal to 5° and an organic masking layer top outersurface roughness proximate the feature pattern at a conclusion of theone etching segment which is characterizable by an average value lessthan 100 Angstroms as is determinable by scanning electron microscopy asan average maximum size of all surface discernible objects of thepatterned masking layer as measured and averaged along any 0.3 micronlength of top outer surface from the one feature pattern, wherein thefeature layer comprises polysilicon.
 21. A plasma etching methodcomprising: forming a patterned inorganic masking layer outwardly of afeature layer to be etched, the patterned inorganic masking layer havingat least one feature pattern having a minimum feature dimension of lessthan or equal to 0.3 micron; and plasma etching the at least one featurepattern into the feature layer using the inorganic masking layer as amask, the plasma etching comprising at least one etching segment whereat least 30% of the thickness of the feature layer is etched using anetching gas comprising one gas compound comprising carbon, hydrogen andat least one halogen present in the etching gas at greater than or equalto 70% concentration by volume as compared to all carbon, hydrogen andhalogen containing gas compounds in the etching gas effective to produceat least that portion of the one feature pattern in the feature layerformed during the one etching segment to have a sidewall taper, if any,of less than or equal to 5°; the at least one etching segment forming anorganic masking layer over the inorganic masking layer, the organicmasking layer having a top outer surface roughness proximate the featurepattern at a conclusion of the one etching segment which ischaracterizable by an average value less than 100 Angstroms as isdeterminable by scanning electron microscopy as an average maximum sizeof all surface discernible objects of the patterned masking layer asmeasured and averaged along any 0.3 micron length of top outer surfacefrom the one feature pattern.
 22. The method of claim 21 wherein theaverage value of roughness is less than or equal to 50 Angstroms. 23.The method of claim 21 wherein the one etching segment comprises highdensity plasma.
 24. The method of claim 21 wherein the one etchingsegment is conducted at the start of said plasma etching and is notconducted throughout all of said plasma etching.
 25. The method of claim21 wherein the one etching segment is conducted at the end of saidplasma etching and is not conducted throughout all of said plasmaetching.
 26. The method of claim 21 wherein the one etching segment isconducted between the start and the end of said plasma etching, and notconducted at the start or end of said plasma etching.
 27. The method ofclaim 21 wherein the plasma etching during the one segment is void ofany etching gases having carbon-nitrogen bonds.
 28. The method of claim21 wherein the plasma etching during the one segment is void of anyetching gases having carbon-oxygen bonds.
 29. The method of claim 21wherein the plasma etching during the one segment is void of any etchinggases having oxygen-oxygen bonds.
 30. A plasma etching methodcomprising: forming a patterned organic masking layer outwardly of afeature layer to be etched, the patterned organic masking layer havingat least one feature pattern having a minimum feature dimension of lessthan or equal to 0.3 micron, the feature layer having a thickness andcomprising polysilicon; and plasma etching the at least one featurepattern into the feature layer using the organic masking layer as amask, the plasma etching comprising at least one etching segment whereat least 30% of the thickness of the feature layer is etched using anetching gas comprising one gas compound comprising carbon, hydrogen andat least one halogen present in the etching gas at greater than or equalto 70% concentration by volume as compared to all carbon, hydrogen andhalogen containing gas compounds in the etching gas effective to produceat least that portion of the one feature pattern in the feature layerformed during the one etching segment to have a sidewall taper, if any,of less than or equal to 5° and an organic masking layer top outersurface roughness proximate the feature pattern at a conclusion of theone etching segment which is characterizable by an average value lessthan 100 Angstroms as an average maximum size of all surface discernibleobjects of the patterned masking layer as averaged along any 0.3 micronlength of top outer surface from the one feature pattern.
 31. The methodof claim 30 wherein the plasma etching comprises only one etchingsegment where 100% of the thickness of the feature layer is etched usingsaid etching gas.
 32. The method of claim 30 wherein the organic maskinglayer comprises photoresist,-the average maximum value of the organiclayer top outer surface roughness being that of the photoresist topouter surface as is determinable by scanning electron microscopy. 33.The method of claim 30 wherein the organic masking layer comprisesphotoresist, and another organic masking material layer formingthereover during the plasma etching, the average maximum value of theorganic layer top outer surface roughness being that of the anotherorganic masking material top outer surface and not that of thephotoresist as is determinable by scanning electron microscopy.
 34. Themethod of claim 30 wherein the one feature pattern comprises a contactopening.
 35. A plasma etching method comprising: forming a patternedorganic masking layer outwardly of a feature layer to be etched, thepatterned organic masking layer having at least one feature patternhaving a minimum feature dimension of less than or equal to 0.3 micron,the feature layer having a thickness; and plasma etching the at leastone feature pattern into the feature layer using the organic maskinglayer as a mask, the plasma etching comprising at least one etchingsegment where at least 30% of the thickness of the feature layer isetched using an etching gas comprising one gas compound comprisingcarbon, hydrogen and at least one halogen present in the etching gas atgreater than or equal to 70% concentration by volume as compared to allcarbon, hydrogen and halogen containing gas compounds in the etching gaseffective to produce at least that portion of the one feature pattern inthe feature layer formed during the one etching segment to have asidewall taper, if any, of less than or equal to 5° and an organicmasking layer top outer surface roughness proximate the feature patternat a conclusion of the one etching segment which is characterizable byan average value less than 100 Angstroms as an average maximum size ofall surface discernible objects of the patterned masking layer asaveraged along any 0.3 micron length of top outer surface from the onefeature pattern, wherein the plasma etching during the one etchingsegment is void of any etching gases having carbon-oxygen bonds, whereinthe organic masking layer comprises photoresist, and another organicmasking material layer forming thereover during the plasma etching, theaverage maximum value of the organic layer top outer surface roughnessbeing that of the another organic masking material top outer surface andnot that of the photoresist as is determinable by scanning electronmicroscopy.
 36. The method of claim 35 wherein the plasma etchingcomprises only one etching segment where 100% of the thickness of thefeature layer is etched using said etching gas.
 37. The method of claim35 wherein the average maximum value of the organic layer top outersurface roughness is that of the photoresist top outer surface as isdeterminable by scanning electron microscopy.
 38. The method of claim 35wherein the one feature pattern comprises a contact opening.